1. Field of the Invention
The present invention relates to a reactor and cooler assembly which is useful for conducting exothermic reactions such as the reaction of molecular oxygen and ethylene to form ethylene oxide.
2. Description of the Prior Art
The oxidation of ethylene to form ethylene oxide is conventionally carried out in a shell and tube reactor. An appropriate solid catalyst comprised of silver is placed in elongated tubes and the reaction gases are passed at reaction conditions into contact with the catalyst. A circulating fluid is provided on the shell side to remove heat generated by the exothermic reaction.
It is important that the reaction gas mixtures be rapidly cooled after completion of the desired reaction in order to minimize the possibility of complete oxidation as well as undesirable side reactions such as formation of formaldehyde and/or acetaldehyde; the formation of such products causes purification problems since they are difficult to separate from product ethylene oxide.
The prior art has recognized this problem and among the suggested remedies has been the use of the last section of the reactor tubes to accomplish cooling of the reactor gases. U.S. Pat. No. 4,061,659 has suggested that a cooling zone be provided adjacent to the reaction zone, the cooling zone being filled with an inert refractory particulate having a surface area of 0.1 m2/g or less.
British patent 1,449,091 provides a tubular reactor which is divided into three distinct zones. The reaction gases pass through tubes which in a first section are packed with inerts to provide a preheat zone, in a second section the tubes are packed with catalyst to provide a reaction zone, and these same tubes in a third section are packed with inert or are unpacked to provide a cooling zone.
U.S. Pat. No. 4,921,681 provides a tubular reactor forming a preheat, reaction, and cooling zone.
More recent U.S. Pat. No. 5,292,904 likewise describes a tubular reactor with the tubes divided into a preheat zone, a reaction zone and a final packed cooling zone.